Partners in the demo databases now have more “correct” VAT regimes,
i.e. which correspond to their country.

For example lino_xl.lib.invoicing.fixtures.demo_bookings was
failing in Lino Voga because there was one enrolment for Alfons
whose invoice_recipient points to Erna, a second enrolment for Erna
directly. The first enrolment returned Erna as Partner, the second
returned her as Pupil. So Lino did not group them and generated two
different items in the plan. Later when executing the plan, the first
item made an invoice for both enrolments, and then on the second
item’s create_invoice() Lino complained that “No invoiceables
found for %s.”.